Question: Which of these numbers is prime? ${3,\ 49,\ 65,\ 85,\ 96}$
Answer: A prime number has exactly two factors: 1 and itself. The factors of 3 are 1 and 3. The factors of 49 are 1, 7, and 49. The factors of 65 are 1, 5, 13, and 65. The factors of 85 are 1, 5, 17, and 85. The factors of 96 are 1, 2, 3, 4, 6, 8, 12, 16, 24, 32, 48, and 96. Thus, 3 is a prime number.